Electric lamp



C. BIRDSEYE ELECTRIC LAMP Jan. 3, 1939.

Filed July 29, 1935 2 Sheets-Sheet l Jan. 3, 1939.

c. BIRDSEYE 2,142,104

Filed July 29, 1935 2 Sheets-Sheet 2 Patented Jan. 3, 1939 UNITED STATESPATENT OFFICE ELECTRIC LAMP Application July 29, 1935, Serial No. 33,694

6 Claims.

The present invention consists in an electric lamp of improvedefficiency and a wider field of use than electric lamps heretoforeknown. It is proposed to restrict the luminous field or beam of the lampwithin predetermined limits where it can be utilized to the bestadvantage and convenience and to concentrate substantially all the lightenergy of the lamp within that field. For example, it is proposed todeflect the light beams which have hitherto been lost in the neck of thelamp and cause them to reinforce the useful beam and in general toreflect the light rays leaving the filament within certain selectedzones so that they shall emerge from the lamp only in its concentratedand useful field.

As herein shown the field or beam of the lamp is defined in part by aperipheral reflecting zone within which the filament is located andwhich serves to restrict the direct rays leaving the lamp to those inthe desired field, cutting'oif those rays which would otherwise causeglare outside this field. While I prefer to utilize silver depositinside the bulb, in certain aspects the invention is not limited inrespect to the character of the reflecting surface employed. Areflecting surface located within the bulb, however, is frequently moreeflicient than an outside reflector and is more securely protected frommechanical injury, so that it is advisable to employ a reflector of thischaracter where conditions permit. The zone of the reflecting surface isso shaped and located as not to cut off any direct rays leaving the lampat the desired angle and so that it will trap substantially no rays byinternal reflection within the bulb, but will direct practically allrays into the intended useful luminous field of the lamp. My inventionis applicable to bulbs intended for both direct and indirect lightingand in both cases it is desirable to limit the reflecting zonesubstantially at the line of maximum bulb diameter; In providing a bulbfor direct lighting, the reflecting zone may extend from the line ofmaximum bulb diameter to a line in the neck of the bulb, while in a lampintended for indirect lighting the refleeting zone may extend from theline of maximum bulb diameter over the entire end of the bulb.

In accordance with the present invention, it is proposed to locate thefilament within the boundary of the reflecting surface so thatpractically all rays emanating from the filament will eventually leavethe bulb in the desired predetermined angle. This might be 60 to thevertical, that is to say, the luminous field of the lamp may comprise a120 cone. On the other hand in a lamp intended for indirect lighting,the filament may be located below the boundary line of the reflectingzone so that the luminous field of the lamp takes the shape of aninverted cone.

I have found that by locating a reflecting disk bulb sizes.

between the filament and the seal of the lamp a noticeable increase inefficiency may be derived. In one aspect, my invention consists in anovel construction for supporting a reflector disk within the electriclamp in the desired position and in such a manner that the disk may beaccurately and reliably retained in place by manufacturing procedurewhich is advantageous from acommerclal standpoint and which requires nounusual amount of skill on the part of the operator. In providing areflecting disk of the desired character serious problems of insulationare encountered; and in another aspect my invention consists in astructure in accordance with which the lead-in wires are insulated fromeach other and from the reflecting disk and carried through the latteron their way to the filament in such a manner as to obviate the dangerof short circuiting. As herein shown the desired results are secured byproviding separate insulating tubes extending in spaced parallelrelation from the press of the stem and passing through separateperforations Provided for that purpose in the reflecting disk. For thepurpose of added rigidity and strength the insulating tubes may be fusedinto the stem press.

Another advantage which may be derived from a reflecting disk of thecharacter above described is that it acts to some extent to seal off theneck of the bulb, or a portion thereof, and so protect the stem, andparticularly the press of the stem, from overheating and consequentdamage.

Another feature of the invention consists in a bulb of oversizeddimensions employed in combination with, one or more of the featuresabove described. The manufacture of electric bulbs has been for manyyears standardized in respect to That is, there is a bulb of standardsize for a lamp consuming 200 watts ofenergy, and a larger size for alamp consuming 300 watts of energy. By employing an oversized bulb, Isecure an increased volume of space about the filament which space tendsto reduce the heating effect of the filament upon the glass both byreason of increased distance therefrom and because of the increasedspace for convection currents in gas filled lamps. Moreover, in anoversized bulb the objectionable tungsten deposit is appreciably dilutedand the heat radiating surface of the bulb and incidental cooling effectis increased. This expedient therefore, tends to prevent overheating anddamage to the material of the reflecting zone, to the glass of the bulb,and to the stem. Another advantage incident to the use of an oversizedbulb is that it permits reclaiming of bulbs by cutting off the neckabove the metallic cap, since in using a commercial oversized bulb thelength of the neck may, without loss of lamp efficiency, be appreciablyreduced in constructing an improved lamp of my invention.

This and other features of the invention will be best understood andappreciated from the following description of certain preferredembodiments thereof, selected for purposesof illustration and shown inthe accompanying drawings, in which,- 1

Fig. 1 is a view in perspective of a lamp embodying my invention,portions of the bulb bee ing broken away,

Fig. 2 is a view in side elevation partly in secinto an enlargedglobular portion. The bulb is provided with the usual sealed-in stem llcontaining an exhaust tube l5 and the lead-in wires It may also beprovided with a threaded l6. brass base I3 of the usual construction.

The bulb herein shown is provided withthe peripheral reflecting surfacel2 which extends from a point somewhat within the neck III .tosubstantially the line of maximum bulb diameter.

The reflecting surface is preferably secured by.

depositing metallic silver upon the inside of the bulb within the area,although the-present invention is not limited to a reflecting surface ofany specific characteristics. The end portion ll of the bulb may befrosted-the frosted portion and the sllvered' portion being separated bya common line of .division so that all the light passing from the bulbmay be diffused by the frosted surface and shadow effects due to theaction of the reflecting surface are obviated.

The stem H has a flattened press atits inner end and.merges into the'filament supporting arbor ll. Arranged at opposite sides of the arborare insulating tubes l1 disposed in spaced parallel relation thereto andherein shown as welded or fused to the end of the stem, although theymay be of other insulating material than glass if desired and may beassociated with thestem or press in any other convenient manner. Thefilament l9 may be supported beyond the end of the arbor I! by anchorwires in the usual manner'and is connected at its ends to lead-in wiresI which pass through the stem and through the insulating tubes I! ontheir way to complete the circuit with the filament, or the arbor may beomitted and a metallic filament support substituted for it.

The light center of the filament l9 as shown in Fig. 2 is located abovethe lower limiting line of the reflecting surface by a distance whichper.-' mits the passage of rays leaving the filament at a downwardlyinclined ngle of about 60 to the vertical. Rays which would otherwisepass from the lamp in a more nearly horizontal direction are arrested bythe reflecting surface and reflected downwardly so that they emerge fromthe frosted surface. ll of the bulb and reinforce or intensify theluminous field of the lamp. As al-.

ready noted, itis desirable to terminate the refiecting zone at the lineof maximum bulb diameter to avoid losing any rays by total internalreflection. It will be understood that the relative location of thefilament and the reflecting surface may be variedin accordance with theuse to-which it is desired to put the lamp. For example, by making aportion of the bulb and the reflector parabolic in shape the light ofthe lamp may be' concentrated in a cylindrical beam and an effectivesearchlight lamp thus provided.

In order to deflect rays which would otherwise pass up into the neck ofthe bulb and become lost it is proposed to employ a reflecting member ofsuitable shape which, as shown in Fig-2, may take the form of a disk Illhaving areflecting surface upon the face toward the filament I 9.

The disk is designed to fill substantially the whole cross-sectionalarea of the neck with only'slight clearance to facilitate insertion ofthe disk and permit expansion whenheated. As herein shown, the disk islocated slightly below the upper line of the reflecting zone and is madeslightly convex downwardly for the purpose of reflecting the light raysreceived from the filament out through the bottom .of the bulb, andpreferably- .withouttendency to bombard the filament with reflectedlight and heat rays. -The reflecting disk may, however, be of-anycontour desired. In Fig. 3-for example, it is shown as' concavedownwardly; but in any case its function is to render effective thoserays which would otherwise be lost in the neck of the bulb and also toact as a shield for the body. of the stem, both by cutting off directheat rays and by sealing the. neck portion of .the bulb against thecirculation of heated gases. 2

A preferred manner of mounting the reflecting disk 20 is shown in Figs.1 and 2.- The disk is. provided with three separate perforations for thepassage of the arbor l8 and the two insulated tubes IT. In constructingthe lamp, the disk?!) 'is threaded upon the arbor ll before the anchorwire button is welded' in place; It is permanently held inv place aboveor within'the ends of the insulating tubes H by a connection with thearbor II which comprises a pair-of .wires 2i insertedon their inner endsin offset relation in the arbor' l8 and clenched at their outer endsover the rim of the disk.

The disk 20 may be of any suitable light re-' fiecting material such assilver, aluminum or porcelain, or it may be of other material andprovided. with a light reflecting surface upon its lower face. with asilver deposit in such areas as to offset the danger of'short-circuiting the lead-in wires.

The filament l9 herein shown may be of 200 watt capacity and the bulbpreferably of large size for such a filament. For example, the bulb,

may be of the standard size regularly employed with a filament of 300watt capacity. The employment of an oversized bulb is important in therespects already touched on. In the first place it affords increaseddistances between the'filament For example, it may be a mica disk andthe glass of the bulb, and increased volume of space about the filament.This is of particular importance in. a lamp having a peripheralrefiecting surface of the characterherein disclosed since it tends toprevent damage to the reflecting surface, even though the latter has a'tendency to increase the temperature at which the whole lamp isoperated. The oversized bulb oflsets this in a favorable degree byincreasing the heat radiating'surface of the bulb; and as a furtherresult the stem is not subjected to dangerous overheating. f

Insome cases however, it may be found advisable to supplement theshielding function of the reflecting member. by providing asupplementary disk of a heat insulating material. Such construction isshown in Fig. 3 where a perforated disk 26 of mica or similar materialis shown as located above a reflecting disk 25 and secured in spacedrelation thereto by anchor wires embedded in the arbor I8. As alsosuggested in this figure the reflector disk 25 may be concave toward thefilament, having a parabolic or other curvature by which the reflectedrays are caused to travel outwardly in a defined beam.

In Fig. 4 I have illustrated my invention as embodied in a lamp designedfor indirect illumination. In this case the neck of the bulb 30 may beunsilvered and the reflecting surface 3| is substantially hemispherical,covering the lower end of the bulb and terminating at its upper edge ina plane transverse to the axis of the bulb, preferably coinciding withthe line of maximum bulb diameter. The intermediate portion 32 of thebulb may be frosted in order to diffuse the light emitted by the lampand eliminate any shadow effect which might otherwise be caused by theaction of the reflector. Where bulbs are to be used in diffusingfixtures it may be unnecessary to frost any areas thereof. As previouslyexplained the reflecting surface is preferably formed by a silverdeposit inside the bulb, but my invention is not limited to this or toany specific reflecting material.

The lamp is provided with the usual base 33 and the sealed-in stem 34through which the leadin wires 36 are introduced into the lamp throughthe press. The arbor 28 is in this case extended to support the filament29 at a point below the upper edge of the reflecting surface 3|. Thefilament may occupy any desired predetermined position, such forexample, that those rays emitted at 60 or more to the axis of the lamp,as shown by the dot and dash line in Fig. 4, pass directly from the bulbwithout reflection, and those emitted from the filament the angles belowthis limit are intercepted and reflected into the same useful zone ofthe luminous field.

In the neck of the lamp shown in Fig. 4 is.

placed a reflecting member, herein shown as comprising a conicalreflector 40 which at its base substantially fills the cross-section ofthe neck of the bulb and is perforated at its apex to permit the passageof the arbor 28. A pair of insulating tubes 31, preferably fused to thepress of the stem, extend downwardly and through perforations providedfor that purpose near the apex of the reflector 40. Except for the threeperforations mentioned, the reflector 40 substantially fills the entireneck of the bulb and acts to reflect outwardly and upwardly those lightrays which would otherwise be lost into the neck of the bulb. The tubes31 serve to insulate the lead-in wires 36 and prevent short-circuitingby the reflector. The reflector may be secured in position in anyconvenient manner, but as herein shown, is fastened to the arbor 28 byanchor wires, which are embedded therein on their inner ends, and may beclenched upon the surface of the reflector at their outer ends. It willbe understood that any suitable insulating device may be employed forconducting the lead-in wires safely through the reflector.

that the stem itself or the button at the end thereof will not besoftened by the excessive heat reflected from the silver upon the wallsof the bulb.

In the case of the lamp of Fig. 4, as in those already described, itwill be noted that the reflector is positioned about the lead-in wires,above and beyond the seal press of the stem so that it is effective as aheat shield for this portion of the stem.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent of the United States is:

1. In an electric lamp including a bulb having a stem and a filamentsupported thereby, a reflector disk located between the filament and thestem seal, and a shield spaced from the rear face of the reflector diskboth the reflector disk and the shield being supported in position uponsaid stem.

2. An electric lamp comprising a bulb having a neck of reduced diameter,a stem mounted.

in the neck of the bulb and perforated for the passage of said arbor andtubes, and oppositely extending arms set in said arbor and clenched overthe rim of the reflecting member to hold it in place in the lamp.

3. An electric lamp comprising a bulb with a neck of reduced diameter, afilament, elongated filament-supporting and insulating members disposedin the neck, and a reflecting member having anchor wires attachedthereto and secured to one of said members.

4. An electric lamp for indirect lighting comprising a bulb having aglobular portion and a neck portion and having a reflecting zoneextending from the tip of said bulb substantially to the line of maximumdiameter of said globular portion, the remainder of said globularportion and said neck portion being translucent; a stem within saidbulb, a filament supported by said stem substantially withinthe boundaryof said reflecting zone, and a conical reflector substantially fillingthe cross-section of said neck portion and so located and of such shapeas to shield said stem and to reflect rays from said filament directlyout through said translucent portion.

5. A gas filled incandescent lamp having a base and a pear-shaped bulbcontaining a coiled tungsten filament and being substantially one sizegreater than the standard sized bulb for the filament employed andhaving a material portion of the bulb coated upon its interior with areflecting surface, and the remainder of the bulb free from suchreflecting surface, the filament being disposed substantially in thefocus of the coated portion of the bulb, and a reflecting member locatedin the bulb between the filament and the base of the lamp.

6. A gas filled incandescent lamp having a base and a pear-shaped bulbcontaining a coiled tungsten filament and having a portion of itssurface coated upon its interior with metallic silver, said portionhaving a radius of curvature substantially the same as the radius ofcurvature of the next size larger pear-shaped bulb for the samefilament, the filaments being disposed substantially in the focus of thecoated portion of the bulb, and a reflecting disk located in the bulbbetween the filament and the base of the lamp.

